1. Field of the Invention
The present invention relates to a cleaning device, a charging device and an image forming apparatus and particularly to a technology of cleaning a charging roller for charging the outer circumferential surface of a photoconductive drum.
2. Description of the Related Art
Nowadays, a charging roller for charging the outer circumferential surface of a photoconductive drum while being held in contact with the photoconductive drum is employed in an electrophotographic image forming apparatus to attain an ozone-less mechanism for charging the photoconductive drum. In this charging system using the charging roller, there is a possibility of causing charging unevenness by the attachment of toner external additive and the like to the outer circumferential surface of the charging roller particularly in the case of a solid-type charging roller having the roller surface thereof ground. To solve this problem, it is known to bring an elastic (spongy) cleaning member into contact with the outer circumferential surface of the charging roller to remove attachments from the roller surface, for example, as disclosed in Japanese Patent Publication No. 3515890. However, if the cleaning member is brought into contact with the roller surface, the toner external additive can be removed from the outer circumferential surface of the charging roller, whereas the toner external additive may be firmly fixed to the roller surface to harm a charging performance, thereby becoming a factor of causing charging unevenness. Accordingly, there have been proposed a charging roller cleaning device for reciprocating a cleaning member to improve a cleaning performance as disclosed in Japanese Unexamined Patent Publication No. H07-199604 and a technology of moving a cleaning member to and away from a charging roller as disclosed in Japanese Unexamined Patent Publication No. H08-22173.
The technologies disclosed in Japanese Unexamined Patent Publications Nos. H07-199604 and H08-22173 improve the cleaning performance of the cleaning device and the durability of the cleaning member in comparison with the charging device disclosed in Japanese Patent Publication No. 3515890, but there is a demand for further improvement in the cleaning performance and the durability.